group status when instrumenting

wish librato would allow us to have a "dynamic instrument" but
without that we need to manually add things
Merge pull request #15 from heroku/pedro-tweak-http-instruments

Group response status when instrumenting
dont assume the user model for helath check
wire up the start of a user api for notificaitons
rename endpoint Producer to ProducerAPI to avoid confusion with the model Producer
Make HerokuClient a class instead of a module
allow heroku client to use other api keys
dont send additional headers when looking up self user account info
add a user auth middleware
update gems
move user api stubbing out so it can be reused
wire up user authenticator middleware and specs
wip start a mediator for listing notifications for a user
Add a notification lister mediator
a working serializer
Simplify the fabricators but at the cost 0.1 seconds to the sepcs
move the seralizer sepc to the seralizer
use the serializer in the endpoint